CSF Shunt Flow Measurement Pad with Control Thermistors
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Solution Overview
Problem
Current methods for determining the flow status or flow rate of cerebrospinal fluid (CSF) in shunts implanted under the skin are either invasive or suffer from inaccuracies due to environmental variations and noise from thermistor signals.
Innovation Solution
A non-invasive apparatus using a pad with multiple temperature sensors, including a shunt-aligned thermistor and symmetrically positioned control thermistors, coupled with a CSF analyzer to process temperature data from a temperature source, providing accurate and repeatable CSF flow rate measurements by minimizing environmental interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single thermistor is used to detect CSF flow, then the detection simplicity is improved, but the measurement precision deteriorates due to environmental variations and noise
Solution Approach 1:
The single thermistor detection method is segmented into multiple thermistors (at least three: one aligned with the shunt and two control thermistors positioned symmetrically). This segmentation allows the system to separate the actual CSF flow signal from environmental noise by comparing the shunt-aligned thermistor readings with the control thermistor readings, thereby improving measurement precision while maintaining operational simplicity.
Solution Approach 2:
Control thermistors are introduced as intermediary elements that do not directly measure CSF flow but instead measure environmental temperature variations. These control thermistors act as mediators that allow the system to subtract environmental noise from the total temperature signal, isolating the true CSF flow-related temperature changes and improving measurement accuracy.
2Measurement precision
If multiple temperature sensors are used to improve measurement accuracy, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent applies local quality by positioning thermistors at specific locations with distinct functional roles: one thermistor is precisely aligned with the shunt to detect CSF flow, while two control thermistors are positioned symmetrically away from the shunt to detect only environmental variations. This localized functional differentiation allows accurate CSF flow measurement without requiring complex sensor arrays, as each sensor has a dedicated, simple measurement task.
Solution Approach 2:
The control thermistors serve multiple functions: they detect environmental temperature variations, provide reference measurements for noise subtraction, and help calibrate the system. This multi-functionality allows the patent to improve measurement precision without proportionally increasing device complexity, as the same control thermistors perform multiple measurement and correction functions.
3Measurement precision
If thermistors are placed close to the shunt for accurate flow detection, then the measurement precision is improved, but the reliability deteriorates due to environmental interference
Solution Approach 1:
Control thermistors are positioned as intermediary elements between the shunt-aligned thermistor and the environmental noise sources. These control thermistors capture environmental temperature variations without being affected by CSF flow, serving as mediators that enable the system to distinguish and separate true flow signals from environmental interference, thereby improving both precision and reliability.
Solution Approach 2:
The system implements feedback by continuously monitoring control thermistor readings and using this information to correct or subtract environmental noise from the shunt-aligned thermistor measurements. This feedback mechanism dynamically adjusts for environmental variations, maintaining reliable and stable flow detection readings even when environmental conditions change.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables quick, non-invasive, and accurate determination of CSF flow status and rate through shunts, improving measurement accuracy and convenience by isolating the temperature signal from the shunt and correcting for environmental effects.
Implementation Method 1
a plurality of temperature sensors (e.g., fast response thermistors) that are aligned in a first direction
Implementation Method 2
when a temperature source (e.g., an ice pack or cube) is applied to the pad
Data Source
AI summary
A method and device for testing for the presence, absence and/or rate of flow in a shunt tubing implanted under the skin by using a measurement pad having a plurality of temperature sensors, one of which is aligned with the shunt and the other sensors being symmetrically displaced on either side of the first temperature sensor in a direction transverse to the shunt tubing. These “outer” temperature sensors act as control temperature sensors. A temperature source, e.g., a cooling agent, positioned within an insulated enclosure, is then applied at a predetermined location on the measurement pad that is insulated from the temperature sensors. The movement of this temperature “pulse” is detected by the shunt-aligned temperature sensor via the shunt tubing as the CSF carries the temperature pulse while the control sensors detect the pulse via convection through the skin. The temperature data from these sensors are provided to a CSF analyzer that determines a CSF shunt flow status or flow rate.